Screening of the Salmonella paratyphi A CMCC 50973 strain outer membrane proteins for the identification of potential vaccine targets

Outer membrane protein antigens usually have strong immunogenicities, closely interact with the immune system and play a significant role in the development of new vaccines. The outer membrane proteins of Salmonella paratyphi A (S. paratyphi A) were screened for immunogenicity and immunoprotection for potential vaccine targets. In this study, the bactericidal effect of antiserum against the total outer membrane proteins of S. paratyphi A CMCC 50973 strain was determined, and their immunoprotection was detected with a challenge experiment on vaccinated mice. The immunogenic outer membrane proteins were identified via immunoproteomic technology, and recombinant outer membrane proteins were expressed and purified. The immunoprotection provided by the immunogenic membrane proteins was verified through active and passive immunity challenge experiments. The result revealed a number of S. paratyphi A outer membrane proteins that were proven as strong protective antigens. Twelve immunogenic outer membrane proteins were located and identified. Five recombinant proteins (LamB, pagC, TolC, nmpC and fadL) with strong immunoprotective abilities were found via the active immunity challenge experiment, with protection rates of 95, 95, 85, 80 and 70%, respectively. They were also proven to induce good immunoprotection via the passive immunity challenge experiment, with protection rates of 65, 55, 60, 55 and 50%, respectively. The immunoprotective rate of the five-antiserum combination was 85%. In conclusion, the LamB, pagC, TolC, nmpC and fadL outer membrane proteins, with strong immunogenicities and immunoprotection, are effective protein candidate targets for the development of new vaccines, whereas the recombinant outer membrane proteins are a promising tool for improving immunoprotection.